• Korean Journal of Optics and Photonics
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• v.18 no.2
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• pp.155-161
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• 2007

A new and simple method of 3-dimensional circuit modeling and analysis is proposed and verified experimentally for the first time by determining 3-dimensional current flow and 2-dimensional light distribution in blue InGaN/GaN multi-quantum well (MQW) light emitting diode (LED) devices. Circuit parameters of the LED consist of the resistance of the metallic film and epitaxial layer, and the intrinsic diode which represents the active region emitting the light. The circuit parameters are extracted from the transmission line model (TLM) and current-voltage relation. We applied the >> proposed method and extracted circuit parameters to obtain the light emission pattern in a top-surface emitting-type LED. The current spreading effect is analyzed theoretically and quantitatively with a variation of the resistance of metallic and epitaxial layers. The emitting-light distribution of the fabricated blue LED showed a good agreement with the analyzed result, which shows the dark emission intensity at the corner of the p-electrode.

• Journal of Korean Society of Forest Science
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• v.97 no.6
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• pp.661-668
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• 2008

This study was conducted to provide the policy information on implementing forestry mechanization through analyzing the project results and policy effectiveness. Study method adopted LISREL (Linear Structural Relationships) model which is the covariance structural equation model. Data was collected by questionnaires on the executors who are actually executing the forestry mechanization project. The analysis results on project outcome, policy satisfaction, and education and training showed the average. But the policy consistency, the consolidation of law and system and the spreading of forest machines showed bellow the average. Therefore, it is necessary to implement the consistent policy through the consolidation of law and system, and to increase the spreading ratio of forest machines in the forestry mechanization. In forestry mechanization project, the policy basis, the spreading of forest machines, and the education and training showed the positive affect on the policy outcome, respectively. The policy outcome had the positive affect on policy satisfaction. Accordingly, although the forestry mechanization policy system is important, it is necessary to spread the forest machines and to increase the training and education of operators for the successful forestry mechanization in the future.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.337-338
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• 2000

The perceptual filter for speech enhancement was analytically derived where the frequency content of the input noisy signal was made the same as that of the estimated clean signal in auditory domain. However, the analytical derivation should rely on the deconvolution associated with the spreading function in the psychoacoustic model, which results in an ill-conditioned problem. In order to cope with the problem associated with the deconvolution, we propose a novel psychoacoustic model based speech enhancement filter whose principle is the same as the perceptual filter, however the filter is derived by a constrained optimization which provides solutions to the ill-conditioned problem.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.166-170
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• 1991

An advanced on-resistance model of VDMOS devices in the low voltage regime is proposed and verified by 2-D device simulations. The model considers the lateral gaussian doping profiles in the channel region and exact current spreading angles in the epitaxial layer for both linear and cellular geometries by employing the conformal mapping. It is found out that the on-resistance of low voltage VDMOS may be overestimated considerably if it is analyzed by the conventional method. The 2-D device simulation results show that the proposed model is valid for all ranges of cell spacings and breakdown voltages.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.6
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• pp.951-957
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• 1994

We present a new model for the series resistance of inverted-staggered amorphous silicon (a-Si) thin film transistors (TFT's) by employing the current spreading under the source and the drain contacts as well as the space charge limited current model. The calculated results based on our model have been in good agreements with the measured data over a wide range of applied voltage, gate-to-source and gate-to-drain overlap length, channel length, and operating temperature. Our model shows that the contribution of the series resistances to the current-voltage (I-V) characteristics of the a-Si TFT in the linear regime is more significant at low drain and high gate voltages, for short channel and small overlap length, and at low operating temperature, which have been verified successfully by the experimental measurements.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.13 no.4
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• pp.291-297
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• 2013

Chaotic dynamics have been studied by many researchers in the fields of biology, physics, and engineering. Interest in chaos is also expanding to the social sciences such as politics, economics, and others, including the prediction of societal events. The concept of leisure has developed from a passive concept correlated with relaxation, entertainment, and ideology formation into a positive concept that assumes a more active role. As information and communications technology develops, digital leisure activity is expected to continue spreading. This expansion of digital leisure function correctly, as well as. Traditional leisure activity functions correctly more, whereas digital leisure activity is predicted to function incorrectly more often. In this paper, we propose a mathematical addiction model of digital leisure that deals with its dysfunctions such as addiction to digital leisure, including computer games, internet search, internet chatting, and social media. Herein, to solve addiction to digital leisure, we propose a model derived from a nicotine addiction.

• The Journal of the Acoustical Society of Korea
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• v.19 no.3E
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• pp.12-18
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• 2000

Psychoacoustic model based methods have recently been introduced in order to enhance speech signals corrupted by ambient noise. In particular, the perceptual filter is analytically derived where the frequency content of the input noisy signal is made the same as that of the estimated clean signal in auditory domain. However, the analytical derivation should rely on the deconvolution associated with the spreading function in the psychoacoustic model, which results in an ill-conditioned problem. In order to cope with the problem associated with the deconvolution, we propose a novel psychoacoustic model based speech enhancement filter whose principle is the same as the perceptual filter, however the filter is derived by a constrained optimization which provides solutions to the ill-conditioned problem. It is demonstrated with artificially generated signals that the proposed filter operates according to the principle. It is shown that superior performance results from the proposed filter over the perceptual filter provided that a clean speech signal is separable from noise.

• The Journal of the Acoustical Society of Korea
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• v.20 no.2E
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• pp.9-16
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• 2001

A psychoacoustic model based noise shaping method which shapes the noise in the frequency domain is proposed, where its presence with a host signal will not be perceptually noticeable. The derivation of imperceptible noise levels from the masking thresholds of the signal involves a deconvolution associated with the spreading function in the psychoacoustic model, which results in an ill-conditioned problem. In this paper, the problem is formulated as a constrained optimization, and it is demonstrated that the solution provides noise shaping where the noise excitation level conforms to the masking thresholds of the signal, and thus the noises embedded in the signal will not be perceived by human ear.

• Proceedings of the IEEK Conference
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• 2000.06a
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• pp.25-28
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• 2000

In this paper, we assume various number of multipaths in one chip duration according to spreading bandwidth. And we take into account of the effects of autocorrelation and relative phases among multipath components within one chip duration, and analyze fading effects. We derive the average error probability for different number of users. Then, we compare the performance of W-CDMA systems with different bandwidths. From the simulation results for different band-widths, wideband CDMA systems show better performance than narrowband CDMA systems in vehicular and pedestrian environments.

• Proceedings of the IEEK Conference
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• 2000.06c
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• pp.125-128
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• 2000

In this paper, we proposed the high quality digital audio watermarking algorithm in the frequency domain. The spread spectrum technique is used to encrypted a stream of information by spreading the data as much of the frequency spectrum as possible. It's technique adapt well to data hiding in audio signal. We have used the perceptual model and MDCT/IMDCT for the high qualify digital audio watermarking. The proposed watermark algorithm preserved high quality audio data from watermark signal.